1. Field of the Invention
This invention relates to an illuminating device and a projector using the same, and is suitable for a color liquid crystal projector for enlarging and projecting, for example, images of three colors displayed on three liquid crystal panels onto a screen.
2. Related Background Art
There have heretofore been proposed various liquid crystal projectors for enlarging and projecting an image made by a liquid crystal light valve or the like onto a screen.
In the projector of this kind, three image display elements are illuminated with three color lights R, G and B obtained by color-separating a light from a light source, and images of three colors R, G and B are displayed by these three image display elements. The images (color lights) by the image display elements are color-combined and are projected onto a screen or the like by a projection lens.
When in this construction, a cross dichroic prism of a construction in which surfaces having dichroic film intersect with each other is used for color combination, there is a case where one of optical path lengths of three color lights for illumination from the light source to the image display elements is longer than the other two optical path lengths or a case where two optical path lengths are longer than remaining one optical path length.
In a projector disclosed in Japanese Laid-Open Patent Application No. 63-116123, an optical path bending plane mirror is provided in the longest one of optical paths of lights of three colors. This is often used in a construction for directing the light from a light source directly to an image display element.
In this case, there has been the problem that in the longest optical path, the light diverges and the utilization efficiency of light is reduced relative to the other short optical paths. Against such a problem, U.S. Pat. No. 5,626,409 discloses a construction as shown in FIG. 9 of the accompanying drawings wherein an illuminating system for illuminating an image display element is provided with a so-called integrator 103 comprising a lens array constructed into the form of a matrix, and a relay system comprising a convex lens and a plane mirror is provided to produce a uniform illuminating area so that a first uniform illuminating area produced in an optical path by the integrator 103 and the image display element may be made conjugate with an optical path longer than the other optical paths in a color separating system.
In FIG. 9, the reference numeral 101 designates a light source such as a metal halide lamp or a mercury lamp. The reference numeral 102 denotes a reflector having a reflecting surface comprising a parabolic surface or an elliptical surface. The reference numeral 103 designates an integrator comprising a first lens array 1031 and a second lens array 1032.
The reference numeral 104 denotes a polarization converting element which converts a non-polarized incident light into a predetermined linearly polarized light and emits it. The reference numeral 105 designates a color separating system comprising dichroic mirrors 1051 and 1052. The reference numerals 1071 and 1072 denote mirrors. The reference numeral 108 designates a relay system having lenses 1081, 1082 and 1083 and mirrors 1084 and 1085.
The reference characters 110R, 110G and 110B denote image display elements for colors R, G and B comprising liquid crystal panels (light valves). The reference numeral 111 designates a cross dichroic prism. The reference numeral 112 denotes a projection lens having positive refractive power and for enlarging and projecting images displayed by the image display elements 110R, 110G and 110B.
The reference numeral 106 designates a condensing lens for condensing the diffused light from the polarization converting element 104 onto the image display elements 110R, 110G and 110B. The reference characters 109G and 109R denote condenser lenses for condensing the illuminating light onto the projection lens, and the lens 1081 of the relay system 108 also has the same role as that of these condenser lenses.
In recent years, in projectors such as color liquid crystal projectors, the downsizing thereof has been desired, and an illuminating optical system for illuminating an image display element has also been downsized. In the case of the color projector as shown in FIG. 9, it is effective for the downsizing of the illuminating system to shorten the longest relay optical path (B optical path) of the optical paths of three color lights.
However, to shorten the optical path of the relay system 108 while maintaining the conjugate relation between the uniform illuminating area formed in the optical path of R and the image display element, the refractive power (positive) of the lenses 1081 and 1082 constituting the relay system 108 must be strong.
The relay system 108 is such that the second relay lens 1082 for adjusting at least the conjugate relation is provided in the central portion of the relay system, the first relay lens 1081 for producing a plurality of light source images produced near the first uniform illuminating area by the lens array 103 near the second relay lens is provided near the uniform illuminating area, the third relay lens 1083 working as a condenser lens for the projection lens in the relay system is provided near the image display element, and the two plane mirrors 1084 and 1085 for bending the optical path are provided between the relay lenses.
Strengthening the refractive power of a lens to shorten the optical path is strengthening the refractive power of the first, second and third relay lenses 1081, 1082 and 1083.
However, if this is done, there is also the problem that the radius of curvature of each relay lens becomes small and the thickness of the lens is increased and the reduction in transmittance by the absorption of the interior of the lens cannot be neglected and after all, the quantity of light is reduced.
It is the object of the present invention to provide an illuminating device and a projector in which a reduction in quantity of light is small.
A first aspect of the present invention is an illuminating device in which a light from a light source separated into three color lights differing in optical path from one another by a color separating system, and light modulating elements conforming to the respective color lights are illuminated with the color lights, wherein at least one of the optical paths of the three color lights has therein an optical system for converging and reflecting the color light passing therethrough without using any converging lens.
A second aspect of the present invention is an illuminating device in the first aspect wherein only the longest one of the three optical paths or only the remaining two optical paths except the shortest optical path have the reflecting system therein.
A third aspect of the present invention is an illuminating device in which a light from a light source is separated into three color lights differing in optical path from one another by a color separating system, and light modulating elements are illuminated with the respective color lights, wherein two of the three optical paths are equal in optical path length to each other and longer in optical path length than the remaining one optical path, and each of the two optical paths has therein an optical system for converging and reflecting the color light passing therethrough without using any converging lens.
A fourth aspect of the present invention is an illuminating device in the first, second or third aspect wherein the reflecting optical system has a plurality of concave mirrors separate from each other or connected to each other.
A fifth aspect of the present invention is an illuminating device in the first, second, third or fourth aspect wherein the reflecting optical system has a concave mirror of a shape free of axis-symmetry (non-rotational symmetry).
A sixth aspect of the present invention is an illuminating device in the first, second, third, fourth or fifth aspect wherein the mirror of the reflecting optical system is formed with a reflecting surface by dielectric material film.
A seventh aspect of the present invention is an illuminating device in any one of the first to sixth aspects wherein polarization converting means for converting the non-polarized light from the light source into a linearly polarized light polarized in a predetermined direction is provided between the light source and the color resolving system.
An eighth aspect of the present invention is a projector having the illuminating device in any one of the first, second and third aspects and a projecting device for projecting a color image by the color light from each of the light modulating elements.
A ninth aspect of the present invention is a projector in which a light from a light source is separated into three color lights differing in optical path from one another by a color separating system, image display elements for displaying images of the colors conforming to the color lights are illuminated with the color lights, the color lights from the three image display elements are combined by a dichroic prism system, and the combined color lights (images) are projected, wherein an optical path longer than the others of the optical paths of the three color lights has therein an optical system for converging and reflecting the color light passing therethrough without using any converging lens.
A tenth aspect of the present invention is a projector in which a light from a light source is separated into three color lights differing in optical path from one another by a color separating system, image display elements for displaying images of the colors conforming to the color lights are illuminated with the color lights, the color lights from the three image display elements are by a dichroic prism system, and the combined color lights (images) are projected, wherein two of the three optical paths are equal in optical path length to each other and longer in optical path length than the remaining one optical path, and each of the two optical paths has therein an optical system for converging and reflecting the color light passing therethrough without using any converging lens.
An eleventh aspect of the present invention is a projector in the aspect of the ninth or tenth aspect wherein the reflecting system has a plurality of concave mirrors separate from each other or connected to each other.
A twelfth aspect of the present invention is a projector in the ninth, tenth or eleventh aspect wherein the reflecting system has a concave mirror of a shape free of axis-symmetry (non-rotational symmetry).
A thirteenth aspect of the present invention is a projector in any one of the ninth to twelfth aspect wherein the mirror of the reflecting system has a reflecting surface of dielectric material film.
A fourteenth aspect of the present invention is a projector in any one of the ninth to thirteenth aspects wherein polarization converting means for converting a non-polarized light from the light source into a linearly polarized light polarized in a predetermined direction is provided between the light source and the color resolving system.
A fifteenth aspect of the present invention is a projector in the fourteenth aspect which has, in the optical path between the light source and the color resolving system, a reflector having a reflecting surface comprising a parabolic surface or an elliptical surface, an integrator comprising a plurality of lens arrays, and the polarization converting element.